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[TGrid] Water Turbine meshed in TurboGrid: Geometry and Topology issues

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Old   September 18, 2014, 18:49
Default Water Turbine meshed in TurboGrid: Geometry and Topology issues
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Abdulaziz Abutunis
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Hi all,
Please I have a couple of question regarding my geometry and topology.

Geometry:




I am simulating a water turbine operating in a river. The turbine has 3 untwisted blades with constant cross-section. The turbine geometry was created using matlab and solidworks. the blade sections was 2D expect the lower one which is attached to the hub. An extra foil was created and attached to the shroud to help trace the shroud curve.
  • Geometry problem
    when the hub, blade, and shroud was imported to TurboGrid, and the shroud tip was created, the blade tip was curved and not flat as i expected. this happened even if I cancel the extra curved foil that attached to the shroud (please see file 1)
  • Topology problems
    - I tried to use the traditional topology (H/J/C/L-Grid), but an error popped up and I do not know why (please see file 2 for the message)
    - I changed to ATM optimized and the topology went with no error, but the topology tip mesh looks shifted form the shroud. The tutorial for the axial fan also has shifted topology but not to much (Pease see file 3).
Please I have another questions regarding using TurboGrid to mesh a water turbine. I have read in another discussion that I can use General Grid Interface (GGI) to take account of the shroud in order to simulate the water turbine but I do not know what is that means.
(http://www.cfd-online.com/Forums/cfx/22798-can-i-use-turbogrid-mesh-wind-turbine-blade.html)

please my last question is can I incorporate another domain with the domain created in TurboGrid e.g. can I surround the turbine passage with cylindrical domain after I import it to ICEM or any other meshing software this to simulate the real water altitude above the water turbine. Also can I extend the rotor passage length; in other words, make the outlet farther downstream to be attached to the outer cylinder.

I appreciate you suggestions

Thank you,

Aziz
Attached Images
File Type: png File 1.PNG (27.5 KB, 76 views)
File Type: jpg File 2.jpg (20.9 KB, 78 views)
File Type: jpg File 3.jpg (16.0 KB, 75 views)
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Old   September 19, 2014, 14:08
Default error solved if blade number increased
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The error message and the topology mesh shift disappeared are caused when I set One-to-One Interface Ranges> Periodic to anything rather than Full. I am still looking for answers regarding the last two question.

Please any ideas are appreciated

thank you

Last edited by ama294; September 24, 2014 at 19:31.
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Old   September 20, 2014, 14:23
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Quote:
Geometry problem
when the hub, blade, and shroud was imported to TurboGrid, and the shroud tip was created, the blade tip was curved and not flat as i expected. this happened even if I cancel the extra curved foil that attached to the shroud (please see file 1)
Do not attach the curved profile at shroud. Just extrude geometry at hub and shroud linearly.


Quote:
- I changed to ATM optimized and the topology went with no error, but the topology tip mesh looks shifted form the shroud. The tutorial for the axial fan also has shifted topology but not to much (Pease see file 3).
This is done to give you best quality. So no worry, after all it is a periodic mesh
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Old   September 21, 2014, 23:35
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[QUOTE] ''Do not attach the curved profile at shroud. Just extrude geometry at hub and shroud linearly.''

Thank you Far for your reply. I extracted linear 3D data for both the hub and shroud. No foil was considered at the shroud, but I still have the same curve blade tip.

thank you though for the suggestion
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Old   September 22, 2014, 00:55
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is it possible to show some images at the blade tip with and without shroud? Please make the shroud transparent and turn on the lines as well...
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Old   September 22, 2014, 12:56
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[QUOTE]''is it possible to show some images at the blade tip with and without shroud? Please make the shroud transparent and turn on the lines as well.''

Hi Far Please see attached

Thank you
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File Type: jpg Shroud.jpg (11.8 KB, 37 views)
File Type: png ShroudTurnedOff.PNG (23.6 KB, 32 views)
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Old   September 22, 2014, 14:11
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geometry seems ok to me
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Old   September 24, 2014, 15:59
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Hi Far I have more couple of questions can I contact you on your email


Thank you,
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Old   September 25, 2014, 01:25
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Hi all I still have problem with the topology mesh.

I used the Traditional Topology method and the topology mesh seems deflected and overlapped at some positions as you can see in the images. This probably because of the small number of blade which caused increase in the passage width . I tried to use control points to fix that but The best I could get is in the images.

Please any suggestion are highly appreciated
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File Type: jpg Capture2.jpg (12.6 KB, 37 views)

Last edited by ama294; September 26, 2014 at 01:20.
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Old   September 26, 2014, 11:55
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I do not know why the control points cannot be created exactly where I place the cursor. For example, if I tried to position the cursor at a node to fix the distortion it would usually jump either to the upper or lower areas.
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Old   September 27, 2014, 17:32
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I have waist a lot of time I think I will go back and use ICEM.
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Old   September 27, 2014, 19:09
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even your problem is not solved using ATM topology?
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Old   September 29, 2014, 14:23
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No the ATM give you a small errors percent but it yielded a negative volume when generating the mesh.
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